Due to their high gravimetric and volumetric energy density, rechargeable lithium ion batteries are interesting for a multiplicity of battery-operated or -supported applications in portable electronic equipment, such as video cameras, laptop computers, mobile telephones and the like, but also for future motor vehicle equipment.
Elemental lithium as the positive electrode material, which is particularly interesting for the achievable energy density for gravimetric and volumetric reasons, is, as is known, associated with inadequate cycle stability of the cells and a considerable safety risk due to the formation of dendrites during charging and discharging.
As an alternative thereto, the system of the "lithium ion" battery, also known as the "rocking chair" battery, has been developed. That system uses electrode materials which can reversibly intercalate lithium both in the negative electrode and in the positive electrode. A carbon-containing material is usually employed as the positive electrode and a lithium-containing mixed oxide as the negative electrode material.
The active negative electrode materials currently preferred are lithium-containing layered oxides of cobalt or nickel, or mixed oxides of these metals. Although galvanic cells which have high energy densities and acceptable cycle stability can be produced using the known negative electrode materials, there continues to be a demand for less expensive and more toxicologically acceptable negative electrode materials. Furthermore, the system-inherent consumption of some of the lithium introduced with the negative electrode material for coating formation on the positive electrode material means that an unequal balance of the active materials is necessary, which can only be partly compensated by special measures, as described, for example, in EP-A 201 038, U.S. Pat. No. 5,162,176 or DE-A 195 28 049.
DE-A 44 35 117 and the specifications cited therein disclose ternary lithium manganese mixed oxides and processes for their preparation, which can be used as inexpensive, non-toxic alternatives to the cobalt and/or nickel compounds. These known mixed oxides are claimed to give cycle-stable electrode materials, but, due to their restricted lithium content, they do not allow adequate compensation for the loss of cyclable lithium. Furthermore, formation of the desired pure spinal crystal structure requires a phase conversion by high-temperature treatment.
Thus, the invention has as an object indicating a process for the preparation of ternary lithium-manganese spinets, and novel ternary lithium-manganese spinels obtainable by this process.